/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *  http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mlizhi.base.codec.net;

import java.io.UnsupportedEncodingException;
import java.util.BitSet;

import com.mlizhi.base.codec.CharEncoding;
import com.mlizhi.base.codec.DecoderException;
import com.mlizhi.base.codec.EncoderException;
import com.mlizhi.base.codec.StringDecoder;
import com.mlizhi.base.codec.StringEncoder;


/**
 * <p>
 * Similar to the Quoted-Printable content-transfer-encoding defined in <a
 * href="http://www.ietf.org/rfc/rfc1521.txt">RFC 1521</a> and designed to allow text containing mostly ASCII
 * characters to be decipherable on an ASCII terminal without decoding.
 * </p>
 * 
 * <p>
 * <a href="http://www.ietf.org/rfc/rfc1522.txt">RFC 1522</a> describes techniques to allow the encoding of non-ASCII
 * text in various portions of a RFC 822 [2] message header, in a manner which is unlikely to confuse existing message
 * handling software.
 * </p>
 * 
 * @see <a href="http://www.ietf.org/rfc/rfc1522.txt">MIME (Multipurpose Internet Mail Extensions) Part Two: Message
 *  Header Extensions for Non-ASCII Text</a>
 * 
 * @author Apache Software Foundation
 * @since 1.3
 * @version $Id: QCodec.java 797857 2009-07-25 23:43:33Z ggregory $
 */
public class QCodec extends RFC1522Codec implements StringEncoder, StringDecoder {
/**
 * The default charset used for string decoding and encoding.
 */
private final String charset;

/**
 * BitSet of printable characters as defined in RFC 1522.
 */
private static final BitSet PRINTABLE_CHARS = new BitSet(256);
// Static initializer for printable chars collection
static {
// alpha characters
PRINTABLE_CHARS.set(' ');
PRINTABLE_CHARS.set('!');
PRINTABLE_CHARS.set('"');
PRINTABLE_CHARS.set('#');
PRINTABLE_CHARS.set('$');
PRINTABLE_CHARS.set('%');
PRINTABLE_CHARS.set('&');
PRINTABLE_CHARS.set('\'');
PRINTABLE_CHARS.set('(');
PRINTABLE_CHARS.set(')');
PRINTABLE_CHARS.set('*');
PRINTABLE_CHARS.set('+');
PRINTABLE_CHARS.set(',');
PRINTABLE_CHARS.set('-');
PRINTABLE_CHARS.set('.');
PRINTABLE_CHARS.set('/');
for (int i = '0'; i <= '9'; i++) {
PRINTABLE_CHARS.set(i);
}
PRINTABLE_CHARS.set(':');
PRINTABLE_CHARS.set(';');
PRINTABLE_CHARS.set('<');
PRINTABLE_CHARS.set('>');
PRINTABLE_CHARS.set('@');
for (int i = 'A'; i <= 'Z'; i++) {
PRINTABLE_CHARS.set(i);
}
PRINTABLE_CHARS.set('[');
PRINTABLE_CHARS.set('\\');
PRINTABLE_CHARS.set(']');
PRINTABLE_CHARS.set('^');
PRINTABLE_CHARS.set('`');
for (int i = 'a'; i <= 'z'; i++) {
PRINTABLE_CHARS.set(i);
}
PRINTABLE_CHARS.set('{');
PRINTABLE_CHARS.set('|');
PRINTABLE_CHARS.set('}');
PRINTABLE_CHARS.set('~');
}

private static final byte BLANK = 32;

private static final byte UNDERSCORE = 95;

private boolean encodeBlanks = false;

/**
 * Default constructor.
 */
public QCodec() {
this(CharEncoding.UTF_8);
}

/**
 * Constructor which allows for the selection of a default charset
 * 
 * @param charset
 *  the default string charset to use.
 * 
 * @see <a href="http://java.sun.com/j2se/1.4.2/docs/api/java/nio/charset/Charset.html">Standard charsets</a>
 */
public QCodec(final String charset) {
super();
this.charset = charset;
}

protected String getEncoding() {
return "Q";
}

protected byte[] doEncoding(byte[] bytes) {
if (bytes == null) {
return null;
}
byte[] data = QuotedPrintableCodec.encodeQuotedPrintable(PRINTABLE_CHARS, bytes);
if (this.encodeBlanks) {
for (int i = 0; i < data.length; i++) {
if (data[i] == BLANK) {
data[i] = UNDERSCORE;
}
}
}
return data;
}

protected byte[] doDecoding(byte[] bytes) throws DecoderException {
if (bytes == null) {
return null;
}
boolean hasUnderscores = false;
for (int i = 0; i < bytes.length; i++) {
if (bytes[i] == UNDERSCORE) {
hasUnderscores = true;
break;
}
}
if (hasUnderscores) {
byte[] tmp = new byte[bytes.length];
for (int i = 0; i < bytes.length; i++) {
byte b = bytes[i];
if (b != UNDERSCORE) {
tmp[i] = b;
} else {
tmp[i] = BLANK;
}
}
return QuotedPrintableCodec.decodeQuotedPrintable(tmp);
} 
return QuotedPrintableCodec.decodeQuotedPrintable(bytes);   
}

/**
 * Encodes a string into its quoted-printable form using the specified charset. Unsafe characters are escaped.
 * 
 * @param pString
 *  string to convert to quoted-printable form
 * @param charset
 *  the charset for pString
 * @return quoted-printable string
 * 
 * @throws EncoderException
 *  thrown if a failure condition is encountered during the encoding process.
 */
public String encode(final String pString, final String charset) throws EncoderException {
if (pString == null) {
return null;
}
try {
return encodeText(pString, charset);
} catch (UnsupportedEncodingException e) {
throw new EncoderException(e.getMessage(), e);
}
}

/**
 * Encodes a string into its quoted-printable form using the default charset. Unsafe characters are escaped.
 * 
 * @param pString
 *  string to convert to quoted-printable form
 * @return quoted-printable string
 * 
 * @throws EncoderException
 *  thrown if a failure condition is encountered during the encoding process.
 */
public String encode(String pString) throws EncoderException {
if (pString == null) {
return null;
}
return encode(pString, getDefaultCharset());
}

/**
 * Decodes a quoted-printable string into its original form. Escaped characters are converted back to their original
 * representation.
 * 
 * @param pString
 *  quoted-printable string to convert into its original form
 * 
 * @return original string
 * 
 * @throws DecoderException
 *  A decoder exception is thrown if a failure condition is encountered during the decode process.
 */
public String decode(String pString) throws DecoderException {
if (pString == null) {
return null;
}
try {
return decodeText(pString);
} catch (UnsupportedEncodingException e) {
throw new DecoderException(e.getMessage(), e);
}
}

/**
 * Encodes an object into its quoted-printable form using the default charset. Unsafe characters are escaped.
 * 
 * @param pObject
 *  object to convert to quoted-printable form
 * @return quoted-printable object
 * 
 * @throws EncoderException
 *  thrown if a failure condition is encountered during the encoding process.
 */
public Object encode(Object pObject) throws EncoderException {
if (pObject == null) {
return null;
} else if (pObject instanceof String) {
return encode((String) pObject);
} else {
throw new EncoderException("Objects of type " + 
  pObject.getClass().getName() + 
  " cannot be encoded using Q codec");
}
}

/**
 * Decodes a quoted-printable object into its original form. Escaped characters are converted back to their original
 * representation.
 * 
 * @param pObject
 *  quoted-printable object to convert into its original form
 * 
 * @return original object
 * 
 * @throws DecoderException
 *  Thrown if the argument is not a <code>String</code>. Thrown if a failure condition is
 *  encountered during the decode process.
 */
public Object decode(Object pObject) throws DecoderException {
if (pObject == null) {
return null;
} else if (pObject instanceof String) {
return decode((String) pObject);
} else {
throw new DecoderException("Objects of type " + 
  pObject.getClass().getName() + 
  " cannot be decoded using Q codec");
}
}

/**
 * The default charset used for string decoding and encoding.
 * 
 * @return the default string charset.
 */
public String getDefaultCharset() {
return this.charset;
}

/**
 * Tests if optional tranformation of SPACE characters is to be used
 * 
 * @return <code>true</code> if SPACE characters are to be transformed, <code>false</code> otherwise
 */
public boolean isEncodeBlanks() {
return this.encodeBlanks;
}

/**
 * Defines whether optional tranformation of SPACE characters is to be used
 * 
 * @param b
 *  <code>true</code> if SPACE characters are to be transformed, <code>false</code> otherwise
 */
public void setEncodeBlanks(boolean b) {
this.encodeBlanks = b;
}
}
